How is fluorine prepared by Dennis method?

Explanation

Preparation of Fluorine by Dennis Method
The apparatus consists of a V-shaped copper tube fitted with copper caps to introduce graphite electrodes and dry `KHF_(2)`.
The electrolyte is dried by keeping it ar `130^(@)C` (403 K) for 48 hours. If electrolyte is moist, oxygen or `OF_(2)` may be produced on passing electric current through molten `KHF_(2).F_(2)` is produced at the anode and `H_(2)` at the cathode.

Preparation of fluorine by Dennes method
`2KHF_(2) to 2K^(+) +4F^(-) +2H^(+)`
At cathode `" "2H^(+)+2e to H_(2)`
At anode `" "4F^(-)-4e to 2F_(2)`
The liberated fluorine gas is passed through U-tubes packed with NaF to absorb the vapours of HF.
`NaF +HF to NaHF_(2)`
Difficulties As fluorine attacks copper to form copper fluoride, the fluorine exit may get blocked. Due to this, fluorine may mix up with hydrogen leading to explosion.